The tailoring of the surfaces of articles to produce nanostructures has been the subject of intense research. When the feature sizes of structured surfaces are significantly less than the wavelength of light (that is, “subwavelength”), valuable optical effects can be realized including, for example, minimization of reflection at interfaces and light extraction.
Known methods for creating the subwavelength surface structure tend to be complicated and expensive batch processes, however. For example, the method disclosed in U.S. Patent Application Pub. No. 2005/0233083 involves bombarding a polymeric surface with Ar/O2 plasma under vacuum conditions of less than 0.5 mTorr. This requirement of extreme vacuum conditions limits the commercial viability of the method. U.S. Pat. No. 4,374,158 describes a gas activation method for creating subwavelength surface structure. This batch process employs a plasma asher to isotropically etch samples in an oxygen-containing gas ambient. The resulting isotropically etched surfaces require an additional coating to provide durability.